Why are the oldest rocks on the ocean floor only 200 million years old while the oldest rocks on the continents are almost 4 billion years old?
Explanation: The oldest oceanic crust is about 260 million years old. This sounds old but is actually very young compared to the oldest continental rocks, which are 4 billion years old. ... It is due to the process of subduction; oceanic crust tends to get colder and denser with age as it spreads off the mid-ocean ridges.